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How It Works
Spiral rib metal pipes use a smooth interior with external ribs for structural strength. Design pressure sums soil, wheel, and vacuum pressures. The thrust equation then converts pressure to force per foot of wall, which must stay below the rib profile's rated capacity.
Example Problem
A 30-inch spiral rib pipe carries soil pressure of 400 lb/ft², wheel pressure of 80 lb/ft², and no vacuum.
- P = 400 + 80 + 0 = 480 lb/ft²
- T = 480 × 30 / 24 = 600 lb/ft
Frequently Asked Questions
What is the advantage of spiral rib over corrugated pipe?
Spiral rib pipes have a smooth interior, giving them better hydraulic flow characteristics and lower friction losses compared to corrugated pipe at the same diameter.
Are spiral rib pipes available in aluminum and steel?
Yes. Aluminum spiral rib is common in drainage applications where corrosion resistance matters. Steel versions are used where higher load capacity is needed, such as under roads.
How is crushing strength different from buckling strength?
Crushing strength refers to compressive failure of the wall profile, while buckling strength addresses the pipe deflecting into an oval shape. Both must be checked for buried pipe design.
Related Calculators
- Buried Corrugated Pipe Calculator — design pressure and thrust for corrugated pipe.
- Pipe Soil Pressure Calculator — soil weight, buoyancy, and load per foot.
- Buried Plastic Pipe Calculator — pressure, thrust, and wall area for plastic pipes.
- Pipe Wheel Loading Calculator — wheel load on buried pipes at various depths.
- Pressure Converter — convert between psi, kPa, bar, and other pressure units.
National Resources Conservation Service. National Engineering Handbook. 1995. USDA.